Modifying Bachmann tram.

Kayanbee

Kayanbee

Registered
14 Sep 2014
21
9
Hampshire
#1
Bachmann Streetcar modifications.



My Bachmann Streetcar never ran very well round my garden so I put some LGB pickup shoes on it. It is quite easily done.



Firstly unscrew the chassis and it will reveal two metal strips one for each side. Solder two small washers on it for the tops of the pickups to go through (LGB part number OLD STYLE 63210) perfectly in line with the cut away section in the chassis. Put a thick washer on the protrusion that goes through the slot in the pickup to bring it further out as much as possible but keeping it in the slot or it with catch on the frogs then secure with as self tapping screw. DO NOT LOSE THE SPRING See Photo.



Whilst it was apart I thought I would upgrade the headlights so I replaced the headlights with 1.8 (or 3mm.) warm white LEDs and replaced the two diodes with 1k resistors. Make sure the LEDs are the connected the correct way round for the direction it is running so you have nice bright headlights.



Whilst I was testing all this out the motor died and that was another problem. Bachmann UK didn't want to know and they said it was am American product. Bachmann America would only supply a complete chassis so the hunt for a motor went on. I found a Mashima SM-MHK 1833 motor from Scale Link which was almost the same size as the Bachmann one and with a bit of carving the old framework it fitted and with some small packing pieces to firm it up. I would recommend the 1B version of this motor as it has 15 mm. shafts as there is more for the worm to fit to although this one was OK. You can get the worm of the old motor with a puller and it fits tightly on the Mashima motor by gently squeezing it in a vice.






 
No72

No72

Registered
21 Dec 2014
221
209
Melobourne Australia
#2
Very interesting. I've never had pickup problems with wheels as I use all of them for current return with trolley pole pickup...
 
chris m01

chris m01

Registered
24 Oct 2009
4,393
361
Birmingham, UK
#3
Mine is battery operated so I removed the trolley pole. The drive mechanism doesn’t seem to be very good on mine. It works ok but....
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
22,947
3,092
North West Norfolk
#4
Very interesting. I've never had pickup problems with wheels as I use all of them for current return with trolley pole pickup...
The trouble outside is that DC without skates requires much cleaner track than DCC with skates - those two options being the extremes. So a DC loco may well perform better with skates simply because you don't have to clean the track quite so frequently - even on the same day if you run into the evening. It's partly because on DC, you're often pushing much lower voltages down the track.
 
No72

No72

Registered
21 Dec 2014
221
209
Melobourne Australia
#5
The trouble outside is that DC without skates requires much cleaner track than DCC with skates - those two options being the extremes. So a DC loco may well perform better with skates simply because you don't have to clean the track quite so frequently - even on the same day if you run into the evening. It's partly because on DC, you're often pushing much lower voltages down the track.
Ok.... Im not a DCC aficionado but my understanding is that an addressable AC signal is superimposed on the DC supply to allow control... So if you were to look at the track voltage on an oscilloscope what would you see? a straight dc line with an AC sine wave on top of it??? Interesting....

When my tramway was outdoors I made a somewhat amazing discovery that if I used 48VAC @ 400hZ with a KPB 3807 rectifier and a LM7812 regulator in each car ( to change to DC and give 12V) the track stayed relatively clean. I got the idea from one of those electronic track cleaner gizmos which are useless outdoors because the voltage is too high and the current tends to leak to earth if things got wet...
 
Rhinochugger

Rhinochugger

Retired Oik
27 Oct 2009
22,947
3,092
North West Norfolk
#6
Ok.... Im not a DCC aficionado but my understanding is that an addressable AC signal is superimposed on the DC supply to allow control... So if you were to look at the track voltage on an oscilloscope what would you see? a straight dc line with an AC sine wave on top of it??? Interesting....

When my tramway was outdoors I made a somewhat amazing discovery that if I used 48VAC @ 400hZ with a KPB 3807 rectifier and a LM7812 regulator in each car ( to change to DC and give 12V) the track stayed relatively clean. I got the idea from one of those electronic track cleaner gizmos which are useless outdoors because the voltage is too high and the current tends to leak to earth if things got wet...
Yeah, my understanding being rather simplistic, but DCC pumps the full 24v out all the time, and that higher voltage gets through a little bit of crud that the DC voltages (at slower speeds) don't.
 
PhilP

PhilP

G Scale, 7/8th's, Electronics
5 Jun 2013
21,272
2,467
Tamworth, Staffs.
#7
Ok.... Im not a DCC aficionado but my understanding is that an addressable AC signal is superimposed on the DC supply to allow control... So if you were to look at the track voltage on an oscilloscope what would you see? a straight dc line with an AC sine wave on top of it??? Interesting....
No.. With DCC 'The signal is the power'..
The signal is a square wave, around zero-volts, of around 22-24 volts peak-to-peak. - there is not (normally) a DC component.

The decoder looks at the control information, then rectifies the signal to DC, and then dependent on the commands in the control-signal generates a PWM output to drive the motor.. - Simple version.. ;)
 
Greg Elmassian

Greg Elmassian

Registered
8 Mar 2014
1,994
514
San Diego
www.elmassian.com
#8
The control information is the modulation of the frequency of the square wave, no AC superimposed on DC (that method is called carrier control).

Thus, even if there is voltage drop, the "control information" is unaffected. A square wave was picked for several reasons, it is easier to decode the modulation and easier to rectify to DC for powering the decoder.

Greg
 
No72

No72

Registered
21 Dec 2014
221
209
Melobourne Australia
#9
That explains a lot as its far easier to create a square wave...